# Stationary Side while Zooming

When changing a layer’s zoom along an axis (leaving the zoom along the other axis unchanged), the sides approach the layer’s center equally. Sometimes though, holding one side stationary as the other side approaches is desirable. This creates an effect that effectively makes it appear as if the image is rotating on an axis so that one edge rotates toward you as the other rotates away. The effect is similar to the Tilt function without the 3D-like change in the size of the layer’s sides or the use of a rotate center change. To create the effect, however, you must override how the program does its thing. We can do that by physically and continuously changing the location of the layer’s center as the layer’s zoom changes to or from 0%. For instance, when the layers zoom reaches 0%, the layer’s center is located at the same location as the layer’s edge.

First, unlock the x and y axes. Locate the little “lock” symbol located to the immediate right of the Zoom-X and Zoom-Y settings and click on it. One of these axes will have a zoom value that will vary to or from 0% zoom.

To make it appear as if the layer is turning from edge-on to face-on, we need to make the layer go from 0% to 100% zoom in the x-axis. So, I would set the x-axis value of keyframe 1 to zero and to 100% on keyframe 2. The other axis is unchanged. While that changes the size, both sides of the layer are moving. To keep one side stationary as the other side approaches, we need to know the pan value (the location on-screen) where the layer side is located. If this value is incorrect as the zoom moves to 0, the side we want to remain stationary will move.

So, the question is, how to find that screen position. There are a number of easy and quick ways to do this. The easiest and quickest way is to get the layer’s width. This is easily accomplished using the equations I developed. See ProShow/Photopia Equations. If you are mathematically challenged, I also have another method that is also easy to use and fairly fast.

What we’re going to do is to use the center marker of a temporary layer as our “ruler.” We will guide it to where we need it and read the pan value of its position to tell us the pan value of the layer’s edge we are going to hold stationary. So, we first add a new layer (gradient or solid). It can be any size you want. The default size I use is 1280×720. I change its opacity to 0% so I can see everything below it. All I need to see is its outline and the icon that identifies where the layer center is. So I need to make sure the Show Layer/Caption Controls is selected. If not, right click over a preview window and select it (it’s a toggled option).

One setting that may be active is the Show Motion Path. For the purpose of finding a layer’s edge, it should be turned off. The icons that identify the layer’s location at each a keyframe only interfere with seeing the layer’s center icon (it’s also known as the rotation center icon). Toggle it off by right clicking over the preview window and clicking on Show Motion Path.

The layer is a 1280×720 layer that is set to a fill frame scale and sized to 50%. It is located at pan 0,0 (screen center).  The “Starting Position” (keyframe 1) settings show that the layer edge is located at Pan-X of -25.

The layer is decreasing in size between keyframes 1 to 3. Here at keyframe 2, the layer has reduced its width by half while the right side has remained stationary. Note that keyframe 2s pan-x value is -12.5 here.

The layer has reduced in width to 0 at keyframe 3. Note that the layer has reduced to 0 width where the layer’s left edge remained. Note that the pan-x indicates -25 here.

Other Options.

Some people advocate duplicating the image layer itself and editing it while referring to the original layer. When you’ve found the right pan location by editing the duplicate layer settings, you would then delete the original layer. The problem with this is method is that it only works if you don’t use modifiers on that layer or any layer that refers to that layer. When you make a duplicate of a layer that refers to other layers (via a modifier), most of the time those references are reset to the duplicate layer itself. If other layers refer to the layer of interest, all references to that layer interest must be found and changed to the duplicate layer. If you don’t do this, all you get is a reference to a once the original layer has been deleted.

Too, if you already have a large number of layers, adding a new one can only add confusion. A duplicate layer goes to the top of the layer stack. You may not want it there and you’ll have to move it back down the stack until its where it belongs. Also, you could end up deleting the wrong layer when it comes time to removing the original layer! However, adding a solid or gradient layer can be made immediately above the layer of interest (thereby reducing the chances of confusing things for yourself!).

You could also use a “measuring” layer that has one axis reduced to 0.25% zoom while keeping the other at 100%. You end up with a line that you would then move around until it is aligned with the edge of the layer of interest. The pan location of that line would then be the pan value used on the layer of interest’s keyframe that has the zoom value of 0%. You just need to make the line’s color distinctive and easy to view (just change the color to a green, red, magenta or some similarly distinctive color when the layer is created). This is effectively the same as using the Measuring Layer above because you’re still using the layer center point to identify the edge of the layer of interest.

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